Before deciding which system you wish to use you may want to consider the differences: Roasting over open coals can take twice as long as it does inside a propane roaster and you will need to be on hand to top up your fire with pre-heated coals ever hour to ensure that you get even cooking and crispy skin.
The general rule of thumb on a BBQ pig is 40-50% meat yield from raw butchered weight. So a 60lb Pig will give you approximately 25-30lb of cooked meat and will feed around 55 people. You’ll need at least 1lb raw weight per person for a mixed group, for a bunch of hungry men I would recommend allowing 1.5lb raw weight per person. If you are cooking over direct heat you may lose the belly meat and as such may need a larger pig. However, if you cook using a rotisserie you will get a better yield and less meat will be lost.
1. Don’t let your guests go hungry, allow at least 1lb raw weight per person. A 100lb Pig will yield approximately 45/50lb of cooked meat.
2. Don't let you pig fall in the fire - ensure that it is securely attached to the roasting pole. With strong clamps including through the spine, avoid using chicken wire and batons.
3. Have an adequate heat source to cook your pig to a safe temperature of 72 deg C in time to feed your guests, ensure that you do not make anybody ill. Roasting over open coals can take one hour or more for every 10lb of meat.
4. You'll need a strong powerful motor to ensure even cooking of your pig: avoid under cooked meat on the inside and burnt wasted meat and inedible skin.
5. Don't make a mess at the party, spilt grease on your deck will not go down well, ensure that you have a large tray to carve up your pig and contain the meat juices.